Back to Basics: Fetch Solr Index Field Name for Sitecore Fields Using Solr FieldNameTranslator

I have been meaning to write this post for a while as I have been using this nifty little feature in all my content search API implementations using the Solr provider.

Unsafe: Defining SearchResultItem classes using hard coded Solr fields names for IndexField data annotation attributes as follows:

[IndexField("page_title")]
public string PageTitle { get; set; }

 Problems:

• Cause runtime errors when field names change in Sitecore
• Hard coded strings, sort of magic values
• Unmanageable code

Safe: Define SearchResultItem classes using strongly typed constants for data annotation attributes as follows:

[IndexField(SampleItem.PageTitleSolrIndexFieldName)]
public string PageTitle { get; set; }

Solution:

• Compile time errors are way better than runtime errors
• More manageable code
• More readable code
• More dynamic query building

Trick: Fetch Solr translated field name values on template fields using FieldNameTranslator and reference them  with code generation.

Step 1: Create a base template to store the Solr Index Field Name under /sitecore/templates/System/Templates/Sections.

Step 2: Inherit the base template onto Template Field template.at /sitecore/templates/System/Templates/Template field

Step 3: Write an ItemSaved event handler that will generate the value for Solr Index Field Name.

using Sitecore.Data;
using Sitecore.Data.Items;
using Sitecore.Data.Managers;
using Sitecore.Diagnostics;
using Sitecore.Events;
using Sitecore.SecurityModel;
using System;
using System.Collections.Generic;

namespace SomeNameSpace
{
    public class ItemSavedEvent
    {
        public string Database { get; set; }

        public void OnItemSaved(object sender, EventArgs args)
        {
            var t = new Dictionary();
            //get the arguments as Sitecore args, and make sure it isn't null
            var eventArgs = args as SitecoreEventArgs;
            Assert.IsNotNull(eventArgs, "eventArgs");

            //grab the current item from the event args, and make sure it isn't null
            var item = eventArgs.Parameters[0] as Item;
            Assert.IsNotNull(item, "item");

            //do not process if the item is not derived from Solr base template inherited on Template Field item
            if (!IsDerived(item, new ID("{2201D7D1-C260-45D1-90AA-5FC1F822417A}")))
            {
                return;
            }

            try
            {
                item = UpdateSolrIndexFieldName(item);
                Log.Info(string.Format("ITEM_SAVE_UPDATE: {0}", item.Fields["Solr Index Field Name"]), this);
            }
            catch (Exception ex)
            {
                Log.Error(string.Format("ITEM_SAVE_EXCEPTION: {0}", ex.Message), this);
            }
        }

        private Item UpdateSolrIndexFieldName(Item item)
        {
            if (item != null)
            {
                try
                {
                    using (new SecurityDisabler())
                    {
                        item.Editing.BeginEdit();
                        try
                        {
                            item["Solr Index Field Name"] = SearchHelper.GetSolrFieldName(item.Name, item.ID);
                        }
                        catch (Exception ex)
                        {
                            Log.Error(string.Format("ITEM_SAVE_EXCEPTION: {0}", ex.Message), this);
                            throw;
                        }
                        finally
                        {
                            item.Editing.EndEdit();
                        }
                    }
                }
                catch (Exception ex)
                {
                    Log.Error(string.Format("ITEM_SAVE_EXCEPTION: {0}", ex.Message), this);
                    throw;
                }
            }

            return item;
        }

        private bool IsDerived(Item item, ID templateId, bool checkSecurity = false)
        {
            if (item == null)
                return false;

            if (templateId.IsNull)
                return false;

            var state = SecurityState.Enabled;
            if (!checkSecurity) state = SecurityState.Disabled;

            using (new SecurityStateSwitcher(state))
            {
                var templateItem = item.Database.Templates[templateId];

                var isDerived = false;
                if (templateItem != null)
                {
                    var template = TemplateManager.GetTemplate(item);
                    if (template == null) return false;
                    isDerived = template.ID == templateItem.ID || template.DescendsFrom(templateItem.ID);
                }

                return isDerived;
            }
        }
    }
}

Here is the cool part that actually fetches the Solr index field name value using FieldNameTranslator from the Solr provider:

using Glass.Mapper.Sc;
using Sitecore.ContentSearch;
using Sitecore.ContentSearch.Linq;
using Sitecore.ContentSearch.Linq.Utilities;
using Sitecore.ContentSearch.SolrProvider;
using Sitecore.Data;
using System;
using System.Collections.Generic;
using System.Linq;
using Sitecore.Data.Items;

namespace SomeNameSpace
{
    public static class SearchHelper
    {
        private static ISearchIndex _masterIndex = SolrContentSearchManager.GetIndex("sitecore_master_index");
        
        public static string GetSolrFieldName(string sitecoreFieldName, ID sitecoreFieldId)
        {
            //for system fields replace double _ with single _ and spaces with empty string
            if (sitecoreFieldName.StartsWith("__")) return sitecoreFieldName.Replace("__", "_").Replace(" ", string.Empty).ToLower();
            var masterDb = Sitecore.Data.Database.GetDatabase("master");

            //get Sitecore field type
            var sitecoreFieldType = masterDb.GetItem(sitecoreFieldId).Fields["Type"].Value;

            //get Sitecore field type name
            var fieldTypeConfiguration = _masterIndex.Configuration.FieldMap.GetFieldConfigurationByFieldTypeName(sitecoreFieldType);
            try
            {
                //convert to system field type
                var type = Type.GetType(fieldTypeConfiguration.Attributes["type"]);

                //get the Solr field name based on the Sitecore field name and Sitecore field type.
                //if fieldNameTranslator is null, you have not configured Solr correctly
                //http://www.sitecorevarun.com/2015/09/resolved-sitecore-solr-provider-error.html
                return _masterIndex.FieldNameTranslator.GetIndexFieldName(sitecoreFieldName, type);
            }
            catch (Exception ex)
            {
                //for all custom sitecore types that are not defined in the field map in default index configuration
                throw ex;
            }
        }
    }
}

Register the event with a patch config.

<configuration>
  <sitecore>
    <events>
      <!-- Custom -->
      <event name="item:saved">
        <handler method="OnItemSaved" type="SomeNameSpace.ItemSavedEvent, SomeBinary">
        </handler>
      </event>
      <!-- END Custom -->
    </events>
  </sitecore>
</configuration>

Step 4: Update your T4 template to generate the code with field names as constants similar to:

 /// SampleItem
 /// 
 /// Path: /sitecore/templates/Sample/Sample Item 
 /// ID: 76036f5e-cbce-46d1-af0a-4143f9b557aa 
 /// 
 [SitecoreType(TemplateId="76036f5e-cbce-46d1-af0a-4143f9b557aa")] //, Cachable = true
 public partial class SampleItem  : GlassBase, ISampleItem 
 {
   public const string TemplateIdString = "76036f5e-cbce-46d1-af0a-4143f9b557aa";
   public static readonly ID TemplateId = new ID(TemplateIdString);
   public const string TemplateName = "Sample Item";
   
     
   public static readonly ID TitleFieldId = new ID("75577384-3c97-45da-a847-81b00500e250");
   public const string TitleFieldName = "Page Title";
   public const string TitleSolrIndexFieldName = "Page_Title_t";
   
   /// 
   /// The Page Title field.
   /// Field Type: Single-Line Text  
   /// Field ID: 75577384-3c97-45da-a847-81b00500e250
   /// Custom Data: 
   /// 
   [global::System.CodeDom.Compiler.GeneratedCodeAttribute("Team Development for Sitecore - GlassItem.tt", "1.0")]
   [SitecoreField(SampleItem.TitleFieldName)]
   public virtual string PageTitle  {get; set;}
     
   
 }

Although Step 4 seems rather straightforward, I am unable to fetch the Solr Index Field Name value using TDS provided T4 templates as follows as it returns an empty value:

public const string <#= GetPropertyName(field) #>SolrIndexFieldName = "<#=GetValue(field.SitecoreFields, "Solr Index Field Name")#>";

If you know a better way to fetch the value in T4 templates, please do share.

hope you find this post useful and as always please leave comments and suggestions for improvements.